1. Field of the Invention
The present invention relates to a film thickness measuring apparatus and more particularly to an apparatus for measuring the thickness of a layer of film on certain material with the use of spectral reflectivity.
2. Description of the Prior Art
To facilitate understanding of the present invention it will be helpful to briefly describe a typical conventional film thickness measuring apparatus of the above-mentioned type below with reference to FIGS. 3 and 4. In these drawings reference numeral 10 generally designates a film thickness measuring apparatus. The film thickness measuring apparatus 10 includes a light source 9, an objective lens system 11, a monochrometer 17, and a photomultiplier tube 19. A microscope 12 which is intended to visually observe the surface of the film layer on the material 16 placed on the sample stage 14 by using an eyepiece 13 and a prism 15.
Incidentally, reference numeral 18 designates a housing section in which the optical measuring system is incorporated.
However, it has been pointed out as a drawback inherent to the conventional film thickness measuring apparatus that an operator should visually observe the surface of the film layer on the material through the eyepiece 13 of the microscope 12 every time film thickness is to be measured and thereby measuring of film thickness can be achieved with necessity for an excessively long period of time.